Directional radio system



Aug. 12, 1941. J. GOLDMANN DIRECTIONAL RADIO SYSTEM Filed Oct. 22, 19583 Sheets-Sheet 1 FiGJ.

MATCHING MEANS MA TCf/l/VG MEANS MATCH/N6 MEANS IN OR J'OACH/M GOLDMANNATTORN EY 1941- J. GOLDMANN 2,251,997

DIRECTIONAL RADIO SYSTEM Filed 001;. 22, 1938 3 Sheets-Sheet 2 KEY/N6JOU/PCE 0/-' RF? MODULATED WIT/7 l000- COURSE L l/VE INVENTOR J'OACH/MGOLDMANN ATTORNEY Aug. 12, 19 41. J. GOLDMANN 2,251,997

DIRECTIONAL RADIO SYSTEM Filed OGb. 22, 1938 3 Sheets-Sheet 5 MODULATED14 /100114150 I W/7'HI200- WIT/1800* FILTER RECEIVER AND DE TE C 70!?800- F/L TE R AUD/BL E INDICATOR 5 CODE COMMUTATOR INVENTOR J OACH/M GOLDNA/WV WOW BY ATTORNEY Patented Aug. 12, 1941 DIRECTIONAL RADIO SYSTENIJoachim Goldmann, Berlin-Wilmersdorf, Germany, assignor to InternationalTelephone De velopment (30., Inc., New York, N. L, a corporation ofDelaware Application October 22, 1938, Serial No. 238,453

(Cl. 250-l1) 11 Claims.

The present invention relates to directional radio systems andparticularly to directional radiating systems suitable for use as courseindicating beacons.

It is an object of my invention to provide a directional array whosepattern is more sharply directed in the vicinity of the course line fora given radiation power than arrays heretofore known.

Another object of my invention is to provide a radio system wherein atransmission network feeds an antenna array comprising two separateantenna means, so as to produce two differently directed radiant actionpatterns each having a distinctive signal and each corresponding toenergization of both the antenna means of the array.

A further object of the invention is to provide an improved lead-inconstruction.

In accordance with one feature of the present invention, two symmetricantenna means are combined into a directional array for producing twodiiferently directed radiation patterns. In the simplest case one meansconsists of a single dipole and the other consists of two dipoles. Bothantenna means are energized for each of the patterns, but the phaserelation between the energization of the two antenna means is differcutfor the two radiation patterns. According to a further feature of theinvention, one of the antenna means comprises an even number of dipolespreferably symmetrically disposed about the course line but energizedasymmetrically. The other antenna means comprises one or more antennaelements symmetrically disposed with respect to the course line and alsosymmetrically energized. The combination of these two patterns resultsin a first pattern of unsymmetric shape with respect to the course line.

If the phase of the physically symmetrical but phasally asymmetric meansare reversed with respect to the phase of the truly symmetrical means, asecond differently directed radiation pattern results which is themirror image of the first pattern. These two patterns are used to definea line of equal intensity which is the desired course line.

According to another feature of the present invention, a directionalantenna array comprising two separate antenna means preferably conjugateto each other at their input terminals, is

energized over a network from two signal sources in such a way that thewaves'from one signal sourceare applied to both antenna means in onephase relationship and the waves of the other signal source are appliedalso to both antenna means but in the opposite phase relationship.

According to a further feature of the present invention, similar antennaarrays and networks are conversely used for a directional receivingsystem giving an action essentially the reverse of the action producedwhen used as a radiation system.

The nature of the invention may best be understood by reference to theattached sheet of drawings, in which Fig. 1 represents, partially inperspective and partially in schematic diagram, a preferred type ofradiation system in accordance with the invention, embodying also apreferred type of antenna array in accordance with the invention;

Fig. 1A illustrates a keying arrangement for use in certain embodimentsof my invention.

Fig. 2 is a polar diagram of the radiation amplitude of the system ofFig. 1;

Figs. 3 and 4 represent, partially in perspective and partially inschematic diagram, alternative forms of systems in accordance with theinvention;

Fig. 5 schematically represents a receiver for use with any of thetransmitting systems of Figs. 1, 3 or 4.

Referring more particularly to Fig. 1, a central dipole I is fed over alead-in line 2 from a sup-- ply system more particularly describedhereinafter. Side dipoles 3 and 4 are symmetrically arranged aboutdipole I along a line perpendicular to the desired course line, thespacing between 3 and 4 being more than A and less than A and beingpreferably 0.92m where A represents a wavelength. These side dipoles arefed over coaxial line 5 and branch lines 6 and i from another point ofthe supply system. The coaxial line 2 which feeds dipole l comprises anouter tubular conductor 23 and an inner tubular conductor 25. Thecoaxial line 5 which feeds the side dipoles 3 and 3 comprises an outertubular conductor 25 and an inner conductor 50. Thus it will be notedthat the tubular conductor 25 serves both as the inner conductor of line2 and as the outer conductor of line 5, as clearly shown in Fig. 1.

In accordance with the present invention, line 2 is coupled to dipole lin a novel manner which simultaneously serves to excite the dipole l ina symmetric manner from the line 2, and also to prevent the passage ofwaves from the lower end of dipole l down over the outer conductor ofline 2. For this purpose the inner conductor 25 of line 2. isconductively connected to the interior quarter wavelengths.

of the hollow dipole I near the central point of the latter, byconductive disc 8 which is connected to the interior of the tubulardipole I and to the exterior of the inner conductor 25 of line 2, asshown. The outer conductor 20 of line 2 is not galvanically connected tothe dipole I in any manner, but merely extends up inside of this dipoleto a point adjacent the disc 8, as shown. By proper adjustment oi theposition of disc 8 and the extent to which tubular conductor 29 extendsinto the dipole I, the coupling between line 2 and dipole I may beadjusted so as to emciently feed. this dipole I in substantially matchedfashion while at the same time substantially suppressing the flow ofwaves from the lower end of the dipole I down over the outer tubularconductor 28 of the line 2.

For the purpose of feeding side dipoles 3 and 4, line 5 is extended upabove the disc 8, and is there connected to branch lines I5 and I, whichin turn extend out through the nodal central point of dipole I to thedipoles 3 and 4. Preferably matching means Sl are provided to match thecombined surge impedances of branch lines 6 and l to the surge impedanceof line 5, and matching means It and II are provided to feed the dipoles3 and 4 in balanced fashion from the coaxial branch lines 6 and I, andif necessary to effect a further impedance match at these points. Thecoupling means I8 and II are connected in diiferent manners so that thephase of energization of dipole 3 is opposite to the phase ofenergization of dipole 3 when these dipoles are excited from the commonline 5. Preferably also either the coupling means 9 or the couplingmeans Ii! and II, or both of these, include sufficient phase delay sothat although the physical separation of the side dipoles is about .92)\as mentioned, the electrical length U from dipole l through couplingmeans II, branch line I, and half of coupling means 9, to the junctionof line 5, and the electrical length W from this junction, through theother half of coupling means 9, branch line 6, and coupling means III tothe dipole 3, are each equal to an odd number of The effect of thisrelationship is that with respect to radiations from dipole I, the sidedipoles 3 and 4 each appear to be effectively open circuited at theircenters, so as to exert practically no influence as parasitic reflectorsupon the radiation pattern of dipole I in the absence of excitation fromline 5. Even if the electrical lengths U and W are not each made equalto an odd number of quarter wavelengths, these lengths should be madeone-half wavelength difierent from each other, preferably by differencesin the connections of the dipoles to coupling means I and I I, so thatwith respect to line dipoles 3 and 4 are oppositely phased, aspreviously mentioned. This opposed. phasing of the two side dipoles withrespect to their feed line insures that this feed line 5 will beconjugate with respect to the dipole I, or in other words insures thatas viewed through lines 2 and 5 the dipole I and the dipoles 3 and 4will be conjugate to each other.

Two further dipoles I and I" are disposed symmetrically about thecentral dipole I at right angles to the side dipoles 3 and 4, i. e.along the desired course line. These further dipoles are not fed'but actas parasitic reflectors. The length of these parasitic dipoles should beapproximately one-half wavelength electrically, these dipoles beingtuned so that they distort the pattern of dipole I to an oblate formhaving its greatest length along the desired course line. Theseparasitic dipoles I' and I" are preferably 0.6 wavelength apart, beingeach 0.3 wavelength from the central dipole. These parasitic dipoles maybe omitted if desired.

In the antenna array shown in Fig. 1, dipole I, together with parasiticdipoles I and I if these are provided, constitutes what may be calledthe truly symmetrical antenna means, and this dipole, or these threedipoles, give a truly symmetrical radiation pattern whose form and phaseboth are alike on the two sides of the course line. The two side dipoles3 and t constitutes what may be called the inversely symmetrical antennameans, since these antennae are disposed symmetrically but energized inopposite phase to produce a radiation pattern whose shape is symmetricabout the course line but corresponding points of which on the two sidesof the course line have opposite phase. The radiation patterns producedby the truly symmetrical and inversely symmetrical antenna meansrespectively, are shown in Fig. 2, the curve a representing the patternof the truly symmetrical means and the curve b that of the inversemeans. With a spacing of 0.93 between the side dipoles 3 and 4 thepattern b has four lobes as shown. With spacings greater than 1.0a thispattern would have more lobes.

In accordance with my invention both antenna means are energized forproducing each of the desired resultant radiation patterns, such aspatterns 0 or d of Fig. 2. For signals which are to be radiated inaccordance with radiation pattern c of Fig. 2, the excitations of thetwo antenna means are so phased that at least in the neighborhood of thecourse line their resulting radiations are substantially cophasal eastof the desired course line and in phase opposition west of the desiredcourse line. For signals to be radiated in accordance with the pattern dof 'Fig. 2, the phase relationship between the excitation. of the twoantenna means is reversed. In order to obtain this phase relationship ofthe radiant action patterns of the two antenna means, the "excitationphases of the dipoles 3 and 4 should differ by from the excitation phaseof the dipole I if the influence of the parasitic dipoles I and I isneglected. If the parasitic dipoles are so tuned that their reradiatingaction lags behind the original radiations from dipole I, this centraldipole I may be correspondingly excited in a slightly advanced phase sothat the total eifective phase of the radiant action pattern it producedby the dipoles I, I and I is 90 from the phases of the dipoles 3 and 4.

Various means may be employed for energizing the truly symmetric and theinversely symmetric antennae means in one phase relationship for signalsto be radiated in accordance with radiation pattern 0 and in theopposite phase relationship for signals to be radiated with theradiation pattern 11. If the signals to be radiated are to bedistinguished by simple Morse code keying such as the well known A-Nkeying extensively used at present, a single source of carrier may beused and simple keying means -may be employed to reverse the relativephases of excitation of the lines 2' and 5' in the rhythm -of theA -Ncode, as shown in Fig. 1A which may be substituted for network I6 andsources I 4 and I5 in Fig. 1. Thus during the time intervals belongingto the A code, dipole I is excited 90 ahead of dipole 4 and 90 afterdipole 3, Whereas during the intervals belonging to the N code, dipole Iis energized 90 ahead of dipole 3 and 90 after dipole 4. In thisdiscussion it is assumed for the sake of simplicity that parasiticdipoles I and I" are omitted or that the phase influence thereof isnegligible. If a coaxial line system such as that shown in Fig. 1 isemployed, the phase reversing means may conveniently be constituted by arelay contact I$A as shown in Fig. 1A which alternately transfers thewaves intended for line 5', over one or the other of two alternate paths5A and 5B whose lengths differ by 180. One single modulated orunmodulated source MA may then serve for giving both signals, thesignals of radiation pattern being distinguished from those of radiationpattern (1 by the rhythm of their keying.

In accordance with the preferred embodiment of the invention, however,the two conjugate antenna means 3-4 and II'I are energized from twoseparate sources of signals distinguished by different carrierfrequencies or preerably by different modulation frequencies asindicated in Fig. 1. Ihese two signal sources I4 and I5 feed the lines 2and 5 through a network i 6 which serves to transfer the signals fromsource I4 cophasally to points I? and I8 of the network, but whichserves to transfer waves from source IE'anti-phasally to these twopoints of the network. The theory of network It may best be understoodby first considering the somewhat simpler systems of Figs. 3 and 4.

In Fig. 3 the antenna array itself is schematically represented as anarray of dipoles fed by simple open wire lines for the sake ofsimplicity, but it will be understood that this antenna array may beactually similar to that of Fig. 1. The branch line 6 is physically andelectrically of length W. The branch line I is physically of the samelength as the branch line 6, but is electrically 180 longer because ofthe transposition shown, the electrical length of this branch line Ithusv being U. As before, U and W differ by 180 and preferably each ofthese lengths is an odd number of quarter wavelengths. The sources I4and I5 of Fig. 3 are illustrated as being the output terminals of twoseparate two-stage modulators, employing plate modulation, and fed by acommon radio frequency source to facilitate the problem of maintainingequal amplitudes. The use of a common radio frequency source alsoresults in a fixed phase relationship between the differently modulatedoutputs of I 4 and I5, but this is not essential for the practice of myinvention.

The network I6 of Fig. 3 is represented as being a pair of transformerspreferably of shielded type connected in the well known hybrid fashion.As shown by the solid and dotted arrowsrespectively, which represent thecurrent directions in the transformers for a positive surge from sourceI4 and a positive surge from source I5 respectively, the source I Ienergizes the lines'2 and 5 cophasally, whereas the source i5 energizesthese lines in phase opposition. The primary of transformer I9 issymmetrically center tapped sothat the same magnitudes of excitation aregiven to the different parts of-the antenna array by a given power fromsource It as-by-the same'power from source I5. The stepdown ratio-ofeach transformer is such as to match the impedances of the modulators tothe impedances of the lines 2 and 5 which are assumed to be matched totheir dipoles.

number of turns on the primary of transformer 2| is for simplicityassumed to be so related to the number of turns on the-primary oftransformer I9 and to the loads imposed on these two transformers by thelines 3 and 5, that sources I and I5 are mutually conjugate. In otherwords, a voltage from source I4 will produce no voltage across theterminals of source I5 or vice versa. Neglecting phase changes producedby I and I the electrical length X is 90 shorter than the sum of theelectrical lengths W and Y, so that in response to waves from source I ldipole I is energized 90 ahead of dipole 3. The system of Fig. 3 issuitable for use with medium or long waves.

In analyzing the network I6 of Fig. 3, it was above pointed out thatwaves from source I4 produce in all parts of the antenna array the samemagnitudes of excitation as would be pro- -'duced by waves from sourceI5 but that the phase relation between the excitations of the twoantenna means when fed from source I4 is the opposite of the phaserelation when fed from source I5. It should also be noted that thisrelationship may be analyzed in another way which is somewhat moreconvenient for use with the other networks later to be described. Forthe purposes of this other analysis, it will be convenient to note atthe outset that whether the two generators I4 and I5 are operating withthe same or with different frequencies, amplitudes, and/or waveforms,the currents or voltages delivered by these generators may be consideredas composed of two pairs of current or voltage components, one pairbeing of the same waveform, amplitude, frequency and phase in bothgenerators, and the other pair of components being of the same waveform,amplitude, and frequency in both generators but being of opposite phasein the two generators. Then those voltage or current components whichare cophasal in these two generators may be designated as signalcomponents Sco while those signal components which are in phaseopposition in the two generators may be designated as $012. It will thenbe noted that with respect to signal Sco all energy is transferred toline 5, whereas the energy of signal components sop is whollytransmitted to line 2.

Referring now to Fig. 4, the antenna array i-3-- l, though it includesonly three dipoles, is of the type having two separate antenna means.One of these means consists of dipole I, and is truly symmetric; and theother of the means comprises dipoles 3, B, and is inversely symmetric.Lines 6 and I are physically of the sa.. e length, but the couplingmeans II couples line I to its antenna Li in the opposite sense from thecoupling, of line 6 to its antenna 3 by coupling means I0. Thus theelectrical length U differs by 180from the corresponding electricallength W just as in the case of Figs. 1 and 3 previously described. Eachof the lengths U and W is again preferably an odd number of quarterwavelengths.

Coupling means I2 serves to feed the dipole I in balanced fashion fromthe unbalanced coaxial line 2, and if necessary also serves to matchimpedances. This coupling means may be generally similar to couplingmeans Ill and II and may be of any well known type. The electricallength Y plus W, including any phase delays in devices 9 and I0, differsfrom the electrical length X, including any phase delays in device I2,by or by an odd-multiple of 90. For convenience The 7 5 it will beassumed that X is 90 shorter than Y plus W ,so that dipole I is excited90 earlier than dipole 3, and 90 later than dipole 4,

Considering now the network I6, and assuming first that a signal Sco isapplied cophasally from sources I4 and I5, it will be clear that withrespect to this cophasal signal component the arms 22 and 23 of thenetwork have substantially no effect since the arm 22 has a length ofA9, and the arm 23 a length of thus making a combined length of onewavelength connected between the points PQ and LM which are assumed tobe cophasally energized. Furthermore, it will also be clear that thepresence of line 2 connected at junction point IT to the two arms 22 and23 will in no way influence the result, since with respect to signalsSee the junction point II represents a voltage node along the arm 22-23and thus no finite impedance connected thereto can have any influence.With respect to cophasal components Soo, therefore, the network may beconsidered as comprising solely the arms 28 and 29, the arms 28 and 21,and the line 5 connected between the last mentioned arms at junctionpoint IS. The signal components S will therefore be wholly fed into line5. It should furthermore be noted that the length of arms 28 and 29 isimmaterial provided it be understood that the components considered asbelonging to the signal Sco are those components which arrive cophasallyat the points PQ and LM rather than the components which leave thegenerators I4 and I5 cophasally'.

With respect to the signal components sop which arrive at points PQ andLM in phase opposition, however, all the energy of these components willbe transmitted to the line 2 over arms 22 and 23. The anti-phasalrelationship of the signal components at PQ and LM will be changed to acophasal relationship because of the fact that arm 23 is one-halfwavelength longer than arm 22. Furthermore, with respect to thesecomponents Sop it is clear that the arms 28 and 21 are ineifectivebecause the sum of the length of these arms 26 and 21 is one-halfwavelength and because these two arms together form a bridging pathbetween points PQ and LM which are traversed by waves of opposite phaseso far as the signal components Sop are concerned. The presence of line5 connected at point I8 between the arms 26 and 21 does not at all alterthe relationship because point I8 is at the midpoint of the halfwavelength bridging path and thus corresponds to a voltage node, so thatit is immaterial what impedances are connected at this point. For thesignal components Sop therefore, the network may be considered asconsisting solely of arms 28 and 29, arms 22 and 23, and line 2connected to the latter arms at junction point II.

It will be clear, therefore, that the bridge I6 of Fig. 4 satisfies thecondition that the signal com ponents S00 arriving cophasally at pointsPQ and LM are wholly transmitted to line 5 while on the contrary theanti-phasally arriving signal components sop are wholly transmitted toline 2. If the effective input impedances of lines 2 and 5 as viewedfrom junction points I? and I8 are alike, the network I6 of Fig. 4 willalso satisfy the further condition that the output terminals ofgenerators I4 and I5 will be mutually conjugate, which is in some casesadvantageous. The division of power between the two antenna means of thecomplete antenna array will also be equal in this latter case, so thatthe signals from each generator will be divided equally between the twoantenna means. 'Such a division of power is in many cases satisfactory.

Referring now to the network I8 of Fig. 1, it will be noted that thisnetwork is in many respects similar to the network I6 of Fig. 4. The arm22 which corresponds to the same arm in the network of Fig. 4 isconnected to line 28 at point Q; and the arm 26 which corresponds to thesame arm in the network of Fig. 4, is likewise connected to line 28 atjunction point P. In the network of Fig. 1, however, the points P and Qdo not coincide but are spaced apart, leaving a small section QP betweenthese two junction points. A further stub section P-R of line 28 extendsbeyond junction point P and is short circuited at its free end R.Although Q is shown as closer to the generator I4 than P, the adjustmentmay be such that the point Q is more remote from the generator thanpoint P. Similarly on the righthand side of the network of Fig. 1, thejunction points L and M are separated from each other thus defining anadditional line section M-L. The length Q-P should preferably equal thelength ML and similarly the length PR should equal the length LN, sothat the network will be symmetrical.

Analyzing the network I6 of Fig. 1, in terms of signal components Scoand Sop, it will be noted that the essential condition that signal Senbe wholly transmitted to junction I8 and Sop be wholly transmitted tojunction I1 is still inherently fulfilled. The input impedances of thenetwork with respect to the two signal components sec and sop, however,may be more or less independently adjusted. With respect to the cophasalcomponent S arms 22 and 23 may be ignored and the junctions of arms 26and 21 may be so adjusted along the lines 28 and 29 that the stubs PRand LN together with the portions of lines 28 and 29 lying between thegenerators and P and L respectively, produce any desired impedancetransformation as to give any desired impedance at the output ofgenerators I4 and I5 with respect to the cophasal signal components.Similarly with respect to the anti-phasal signal components, theposition of junctions Q and M may be adjusted so that the stubs QR andMN together with the sections of lines 23 and 29 lying between thegenerators and points Q and M, will give the desired impedancetransformation for the anti-phasal components.

It is true that the adjustments of impedances for component Sco are notwholly independent of the impedance adjustments for component sop in thenetwork shown, since the total length from R to generator I4 is fixed assoon as the length PR and the length from P to generator I4 isdetermined. Nevertheless the adjustments shown are sufficient to obtainany desired ratio between the impedances with respect to Sco and Sop.Thus by properly adjusting the lengths R-P, P-Q and Q-HI, as Well as thecorresponding lengths on the righthand side of the network, the powerdistribution between the two antenna means may be varied to any desiredratio. At the same time the impedance presented to the generators I4 andI5 by the network may ordinarily be made to assume a convenient value;and exact matching between the generators and the network may beaccomplished in the output circuit of the generator. Alternatively,further matching means may be inserted beyond junction 11 or beyondjunction I8 in the lines 2' and 5' which are individual to the separateantenna means, thus providing completely independent matchingadjustments for the cophasal and anti-phasal signals.

The junction points I! and I8 of the network l6 of Fig. 1 are connectedto the lines 2 and 5 by way of lines 2' and 5' as shown. Where the line5 couples to the line 5 a short-circuited stub 52 of 4% electricallength is provided outside of the line 5' so as to avoidshort-circuiting the line 2. The line 2 is connected to the line 2 indirect fashion, suitably through a tapered junction if it is desired tomaintain line 2' of the same diameter as line 5'.

Although the simplest embodiments of my invention comprise in the trulysymmetric means only a single dipole, or in a single dipole withparasitic reflectors, satisfactory results may also be obtained by theuse of a plurality of fed dipoles for the truly symmetric antenna means.In fact, a greater number of dipoles than the number shown may be usedin either or both of the means provided only that the number of dipolesin the inversely symmetric means should be an even number. In order toobtain a particularly advantageous sharp pattern such as shown in Fig.2,

the inversely symmetric means should in itself 7 produce a patternhaving at least four lobes and for this purpose should comprise at leastone pair of dipoles spaced more than apart, their separation beingpreferably at least In accordance with my invention, moreover, thisinversely symmetric means preferably comprises at least two dipoles,which may or may not be the same pair just mentioned, whose separationis less than one wavelength. If the dipoles which are spaced more thanare more than 1.0x apart the pattern b will have more than four lobes.It is then desirable to further provide another pair of dipoles spacedless than one wavelength apart and fed with sufficient power to shapethe radiant action pattern produced by the inversely symmetric meansalone so that this pattern has no directions of zero intensity exceptalong the axis of symmetry thus preventing the formation of falsecourses.

Although the novel method of feeding two antenna means by means of anetwork such as the network It of Figs. 1, 3 or 4, is particularlyadvantageous in connection with the novel antenna array of my invention,this same general method of feeding may also be employed with certainother types of antenna systems. In particular the feeding system of myinvention may be applied to an antenna system consisting of a loop and acentrally disposed dipole, line 2 of Fig. 3

being used for example to feed the loop and line 5 I of this figurebeing used to feed the central dipole. Other antenna arrays having twomutually conjugate antenna means are also suitable for excitation withthe novel feeding system of my invention.

It should also be understood that other types of networks than thenetworks It of Figs. 1, 3 and 4 may be employed, for example, aWheatstone type bridge of resistance or reactance elements may be fedacross its conjugate diagonals from sources It and i5, and the poweracross two adjacent arms of this bridge may be applied to the twoantenna families. In such a case the bridge arms which feed the antennaemay preferably be constituted by the primaries of transformers to thesecondaries of which the antennae are connected.

In the preferred embodiment of my invention the sources M and i5 supplysignals of the same N frequency and preferably the same amplitude butmodulated with different modulation frequencies, the modulation depthbeing the same for both signals. Although the antenna arrays abovedescribed are symmetric, not only about the course line but also about aline perpendicular thereto, satisfactory patterns may be produced witharrays which are asymmetric about either or both of these lines.Asymmetry about the line perpendicular to the course line is especiallydesirable when it is desired to define a course extending predominantlyin one direction from the array.

Any of the systems above described may, in accordance with my invention,be employed in converse manner as directional receiving systems. InFigs. 1, 3 or 1, for example, sources l4 and i5 may be replaced byseparate or partially separate receivers, preferably with means forindicating the relative intensities of signals incoming over lines 23and 29. Signals from a transmitter on the course line will come in onlines 28 and 29 with equal intensity. Signals from a transmitter not onthe course line will come in with different intensities on lines 28 and29.

If desired, network 1 6 may be omitted and lines 2 and 5 may beconnected to one common receiver through suitable keying means such asdescribed in connection with Fig. 1 for reversing the connections fromline 2 (or from line 5) in A-N timing. The use of a network It as shownin Figs. 1, 3 or 4, is, however, preferred even when the system isemployed for receiving since it obviates the need of moving parts.

In a receiving system also a network such as it of Figs. 1, 3 or 4 maybe used with certain other types of antenna arrays than the novel typeof array provided by my invention. For example, a dipole and a loopsymmetric thereto may be connected to junctions l1 and E3 of a networki6 and separate or partially separate receivers may then be connected tolines 28 and 29.

The radiations from my preferred form of beacon comprise two separateradiation patterns such as c and d of Fig. 2, one of these patternscorresponding to signals modulated with one modulation frequency and theother pattern corresponding to signals modulated with the othermodulation frequency. Such signals are well adapted for reception byreceivers of the tuned reed type for giving a visual indication.

In case it is desired to receive such. frequency modulated signals so asto give an indication of the AN type similar to that ordinarily-given byreceivers responding to keyed course beacon transmitters, th specialreceiving arrangement of Fig. 5 is particularly useful. As shown in thisfigure a receiving antenna 35 delivers waves to a receiver and detectorSI of known type, the output of this receiver and detector beingseparated by filters 32 and 33 which are tuned to the modulatingfrequencies respectively as indicated. The outputs of these separatingfilters are then rectified by rectifiers 34 and 35 as shown andconnected in opposed fashion to a sensitive current or voltageindicating instrument 36 which serves as a visual indicator. If thevisual indicator 36 cannot readily be center tapped a shunt may beconnected around it, the center point of which is grounded, or theleakage of rectifiers 3d and 35 in a backward direction may be reliedupon for completing the circuit of current through the visual indicator.

This equipment will in itself serve as a visual indicating receivingarrangement for use with frequency modulated signals of the typedelivered by various transmitter arrangements of Figs. 1, 3 and 4. Forthe purpose of further providing audible indications of the commonlyaccepted A-N type, a vacuum tube 31 may be connected up in well knownfashion to form an audio frequency oscillation generator as shown, theoutput of this generator being supplied to an audible indicator 38. Amodulating tube 39 whose anode is fed in parallel with the anode of tube31 through the common impedance 40 is connected as shown to modulate theoscillations of tube 31 by plate modulation in well known manner. Trapcircuit 4| is provided to prevent the flow of the oscillation frequencyinto tube 39. In order to produce the A-N code effect a code commutatoror interruptor contact arrangement 42 is provided. This code commutatormay be operated by clock work or in any other well known manner, andserves to connect the grid of modulating tube 39 alternately to one sideand then to the other side of visual indicator 33 with a coded timingcorresponding to the Morse code for A and N. Thus the grid of modulator39 is connected to the lower side of indicator 36 during intervalscorresponding to the Morse code letter A and is connected to the upperside of indicator 36 during the intervals corresponding to the Morsecode letter N, these intervals being intermeshed in well known manner sothat at all times the grid of modulator 39 is connected to one or theother side of the indicator. In order to reduce key clicks it may bedesirable to make the contact of commutator 42 make-before-break, and inthis case resistors 43 and 44 may be provided to preventshort-circuiting of the visual indicator during the transfer of themake-before-break contact arrangement.

The operation of the receiver is as follows: If the signals modulatedwith one frequency such as 800 cycles are received with the sameintensity as the signals modulated with the other frequency, say 1200cycles per second, the voltages delivered by rectifiers 34 and 35 willbe equal and the visual indicator 36 will not be deflected. At the sametime the voltages applied to the grid of 39 will remain constantregardless of the movement of commutator 42, and thus the tone producedby generator 31 in the earphones 38 will be of constant intensity, thussimulating the continuous dash signal ordinarily heard on the courseline.

If the receiving arrangement is moved to a position where the 1200 cyclemodulated signals predominate over the 800 cycle modulated signals, theoutput of rectifier 34 will exceed that of rectifier 35, and a currentwill flow downward through the visual indicator 36 suitably deflectingthe latter. At the same time the voltag applied to the grid of modulator33 when the contact arrangement of commutator 42 is in its righthandposition will be more positive than the corresponding voltage on thegrid when the contact arrangement is in its lefthand position. Modulator39 will draw more current during the intervals when the contact ofthe/code commutator is in its right-hand position, i. e. during theintervals corresponding to the N code. The voltage supplied tooscillating generator 31 will thus be greater during the intervals whenthe code commutator is in its lefthand position, i. e. during theintervals corresponding to the Morse code letter A. The audible tonedelivered to the earphones 38 will therefore exhibit periodic increasesin loudness in accordance with the timing corresponding to the Morsecode letter A. Thus a downward current through the indicator 36 and aloudness increas corresponding to the code A in earphone 38 bothrepresent a predominance of signals modulated with 800 cycles persecond.

In similar fashion if the signals modulated with 800 cycles per secondpredominate, an upward current will flow through the visual indicator 36and the tone in earphones 38 will periodically increase in the timing ofthe Morse code letter N.

Although I have described and shown certain embodiments of my inventionfor the purposes of illustration, it will be understood thatmodifications, adaptations and variations thereof occurring to oneskilled in the art may be made without departing from the scope of theinvention as defined in the appended claims.

What I claim is:

l. A directional antenna array comprising first antenna meanssymmetrically disposed with respect to a desired course line, secondantenna means comprising an antenna element on each side of said courseline, said elements being spaced apart more than of a wavelength at theoperating frequency, and two translating means separately coupled inlike phase relation to said antenna means and in different phaserelation to said antenna elements to produce radiant action inaccordance with two overlapping patterns.

2. An array according to claim 1, wherein said second antenna meansincludes at least two elements on opposite sides of said course line andspaced apart less than one wavelength at said operating frequency.

3. A network for transferring high frequency Wave energy between twowave translating equipments and two pairs of terminals for cooperativeinteraction, comprising two lines each an odd number of quarterwavelengths long and differing in length by an odd multiple of a halfwavelength, said lines being connected to respectively couple said twoequipments to said first pair of terminals, and two other lines each anodd number of quarter wavelengths long and differing in length by aneven multiple of a half wavelength, said last mentioned lines beingconnected to respectively couple said two equipments to said second pairof terminals.

4. A directional radio system comprising wave translating means fortranslating two separate sets of signal waves, first antenna meanssymmetrically disposed with respect to a desired course line, secondantenna means comprising two antenna elements symmetrically disposedabout said line and spaced more than of a wavelength apart at theoperating frequency, transmission means for coupling both said antennameans with said wave translating means in one phase relationship for oneof said sets of signal waves and for coupling both of said antenna meanswith said translating means in a different phase relationship for saidsecond set of signal waves.

5. System according to claim 4, wherein said wave translating meanscomprise two separate channels for said separate sets of signal waves,and wherein said transmission means comprises a network coupled to saidtwo channels and having a first pair of points conjugate to said twochannels with respect to wave components passing cophasally and equallyover said channels, and a second pair of points conjugate to said twochannels with respect to wave components passing antiphasally andequally over said channels, said first antenna means being coupledacross said one of said pairs of points and said second antenna meansbeing coupled across the other of said pairs of points.

6. System according to claim 4, wherein said wave translating meanscomprise one common channel for both said sets of signal waves, andwherein said transmission means comprises keying means for coupling bothsaid first and second antenna means with said common channel in onephase relationship during certain time intervals and coupling both saidfirst and second antenna means with said common channel in a differentphase relationship during other time intervals.

7. A directional radio system comprising first and second mutuallyconjugate antenna means, two wave translating equipments, a networkcoupled to said equipments, a first pair of points of said network beingconjugate to said equipments with respect to wave components passingcophasally and equally through said equipments but in energy transferrelation to'said equipments with respect to antiphasal components, and asecond pair of points of said network being conjugate to said equipmentswith respect to wave components passing antiphasally and equally throughsaid equipments but in energy transfer relation to said equipments withrespect to cophasal components, connections between one at said pairs ofpoints and said first antenna means, and connections between the otherof said pairs of points and said second antenna means.

8. A system according to claim 7, wherein said network coupled to saidequipments comprises a first winding having two parts, a second winding,said second winding and one part of said first winding being seriallyconnected across one of said equipments and said second winding, and theother part of said first winding being serially connected across theother of said equipments, and an additional winding coupled to said twoparts so as to respond oppositely to currents through said twoequipments which traverse said second winding in the same sense.

9. A system according to claim 7, wherein said network coupled to saidequipments comprises two lines each an odd number of quarter wavelengthslong and differing in length by an odd multiple of a half wavelength,said lines being connected to respectively couple said two equipments tosaid first pair of points, and two other lines each an odd number ofquarter wavelengths long and differing in length by an even multiple ofa half wavelength, said last mentioned lines being connected torespectively couple said two equipments to said second pair of points.

10. A beacon for guiding airplanes along a desired path which comprisesfirst antenna means for producing a first pattern of a given frequencyshaped with at least four lobes and having oppositely shaped componentson the two sides of said path, second antenna means for simultaneouslyproducing a further pattern of said same frequency having like phasedcomponents on the two sides of said path, means for deriving one set ofsignals from said first and second antenna means by coupling saidantenna means in one phase relation with respect to one set of signalsand deriving energy from said first and second antenna means by couplingsaid antenna means in a different phase relation with respect to anotherset of signals, and means for comparing said derived energies.

11. A beacon for guiding airplanes along a desired path which comprisesfirst antenna means for producing a first pattern of a given frequencyshaped with at least four lobes and having oppositely shaped componentson the two sides of said path, second antenna means for simultaneouslyproducing a further pattern of said same frequency having like phasedcomponents on the two sides of said path, and means for energizing saidfirst and second antenna means in one phase relation with one set ofsignals and energizing said first and second antenna means in adifferent phase relation with another set of signals.

JOACHIM GOLDMANN.

